A model to describe the distribution of photosynthetically active radiation in forests using 3D point cloud data

Abstract

The invention provides a model for depicting the distribution of photosynthetically active radiation (PAR) in a forest by using three-dimensional point cloud data, which belongs to the research field of vegetation remote sensing modeling. Aiming at the problem that the three-dimensional distribution of forest canopy PAR cannot be effectively estimated by using lidar data on a fine scale at present, the present invention proposes a forest PAR three-dimensional spatiotemporal distribution estimation model based on the forest ground lidar data obtained from multiple stations. The model separately considers direct solar and scattered PAR transport in the forest, while taking into account the effects of element angles. The model constructed by the invention can quantitatively describe the three-dimensional space-time distribution of PAR in the forest on a fine scale, with high precision, which is helpful for the research on the physiological process of the forest.

Description

1. Technical field [0001] The invention is a model for depicting the three-dimensional space-time distribution of forest photosynthetically active radiation on a fine scale through three-dimensional point cloud data. Estimating the three-dimensional distribution of forest photosynthetically active radiation at any time belongs to the research field of vegetation remote sensing modeling. 2. Background technology [0002] Photosynthetically active radiation (PAR) refers to the part of solar radiation with a wavelength between 400-700 nm that can drive vegetation to carry out photosynthesis, and is an important environmental factor affecting vegetation photosynthesis and transpiration. The difference in PAR received by different positions of the forest canopy is obvious, and this difference changes with the change of the position of the sun. At the same time, the leaf photosynthetic speed has a nonlinear response to PAR. Therefore, the three-dimensional spatiotemporal distribut...

AI Technical Summary

Problems solved by technology

First of all, Bell's law is only applicable to the case of random distribution of elements, which has limitations

Second, the density of ALS data points is low, which cannot accurately describe the three-dimensional spatio-temporal distribution of forest canopy PAR

At the same time, since the photosynthetic efficiency of vegetation under diffuse PAR conditions is higher than that under direct PAR conditions, it is necessary to consider the transmission process of direct sunlight and diffuse PAR inside the canopy separately, but many studies have not considered this factor

In addition, the PAR on the surface of canopy elements is affected by the angle between the normal vector of the element and the incident direction of the sun. The smaller the angle, the larger the cut-off area of ​​the element, and the larger the surface PAR. However, LiDAR data is currently used to describe the three-dimensional distribution of canopy PAR The study failed to take into account the influence of the angular distribution of the true elements of the canopy

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